updated 11:25 pm EDT, Tue March 22, 2011

We test the T-Mobile Sidekick 4G at CTIA

When T-Mobile unveiled the Sidekick 4G, fears immediately surfaced that the switch to Android killed what the now defunct Danger had done to make the Sidekick special, such as jump keys. Those concerns are certainly valid, but the carrier is counting on a custom interface and surprisingly high-end specs to make up the difference. Read on for an early take on whether they've reached that goal.

The physical design is somewhat reminiscent of a definitive model of the messaging slider, like the Sidekick LX, but has conspicuous changes. Apart from the Android controls, there's now a jump button that, like the old Sidekick, jumps to where you want to go when joined with a letter key: jump + G takes you to the photo gallery, for example. All of the buttons are large, physical buttons, which introduces a chance for wear but is also more satisfying and easy to hit.

The design is fairly thick. We're not certain about the slider. It's easy to slide out, but it doesn't tuck back in as easily and usually requires a deliberate and (for now) not entirely natural push to go back down. That said, we never felt it was going to break after repeated use.

Our views on the keyboard were mixed. It's fairly easy to type quickly, and it has short key travel without losing feel like on the HTC Merge, but we noticed ourselves accidentally hitting wrong characters in our minutes of testing. We suspect that it's a matter of practice, although we haven't had that issue with others.

It's in software that the Sidekick 4G shines more. The Sidekick optimizations are relatively spare: it mostly revolves around a jump menu, which involves hitting the key by itself, and subtle changes to how you launch different sections on the home screen. T-Mobile is using a very stylized, almost Zune-like giant text metaphor, and it works both for quick navigation and for simply setting the Sidekick apart. There's a Mini Diary for recounting a personal history through text and photos, but overall it feels more like an Android phone with Sidekick on top than the opposite.

That's not necessarily a bad thing. Compared to even a Galaxy S 4G, the Sidekick's interface is surprisingly uncluttered and easy to navigate. It's still Android 2.2 underneath. Still, the light touch makes it very fast, and the 21Mbps HSPA+ 3G pulls down pages almost at Wi-Fi speeds, even on the same 1GHz Hummingbird processor that's been use in far slower devices for months. We like that the messaging is appropriately front and center on the stock home screen.

One note about the media player: it has Slacker radio built-in, which to us is a big help for discovering new music or just setting and forgetting music instead of picking every track.

We're most eager to know the pricing, since that could well dictate how the Sidekick 4G survives. Classic Sidekicks were more expensive than many remember, but they also weren't attached to $30 data plans. If the Sidekick 4G could be had on a $10 data plan, it could catch on quite easily for the messaging crowd or parents getting their teens "real" smartphones. A full price, however, would treat it just like any other smartphone and risk losing it in a sea of other Android messaging phones. We'll know more later in the spring, when it ships.